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(11) | EP 1 518 609 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
| published in accordance with Art. 158(3) EPC |
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| (54) | METHOD OF DECORATING METAL PARTS THROUGH THE APPLICATION OF A POWDER PAINT |
| (57) The present invention comprises a procedure for the decoration of metallic pieces
in general, and in a preferred manner of aluminium profiles to which it is sought
to apply a decorative coat imitating a natural finish such as marble, wood, etc. It
is the object of the present invention to provide a procedure for decoration in which
the decorative motif can be reproduced with great precision and therefore offer a
finish of very high quality, and at the same time permit the pieces to be treated
to be manipulated during the decoration stage without this affecting the final quality
of the decorative effect. The present invention has its application in the field of
decorating metallic pieces, and in particular in the decoration of aluminium or iron
profiles by means of the application of powder paints. |
OBJECT OF THE INVENTION
[0001] The present invention comprises a procedure for the decoration of metallic pieces in general, and preferably of aluminium or iron profiles to which it is desired to apply a decorative coat imitating a natural finish such as marble, wood, etc.
[0002] The object of the present invention is to provide a procedure for decoration in which the decorative motif can be reproduced with great precision offering therefore a very high quality finish, and at the same time permitting that the pieces to be treated can be manipulated during the decoration stage without this affecting the final quality of the decorative effect.
[0003] The present invention is of application in the field of decorating metallic pieces, and in particular in the decoration of aluminium or iron profiles by means of the application of powder paints.
BACKGROUND OF THE INVENTION
[0004] The use of aluminium profiles for the production of windows, doors and other enclosures, has to a great extent replaced the employment of wood due to their lower cost and to their structural and manufacturing advantages.
[0005] There have been multiple attempts to achieve a decorative finish of aluminium as similar as possible to wood, however none of these attempts has produced a satisfactory result.
[0006] One of these first attempts is that described in the Japanese patent JP-4318195 which presents an electrolytic procedure for the decoration of aluminium, by means of which the final finish obtained is very resistant to weather conditions, however the quality of the decorative effect is very far from being acceptable.
[0007] Other known systems are based on the employment of the technique known as "sublimation" widely employed in the textile industry, which has allowed the quality of the decorative appearance to be perfected considerably, but the resistance of their colours to light and their high cost have resulted in a limitation of their application.
[0008] Other known techniques of decoration are those described in the European patents EP-0.843.598 and EP-0.656.231, based on the application of paint on paint, wherein the problems of cost and of resistance to light have been resolved, but they have not achieved a decorative appearance with sufficient precision to reproduce satisfactorily the appearance of wood.
[0009] Another example of this type of procedure is that disclosed in the European patent EP-0.818.248 based on the application of screen printing with powder paint, but which has not resolved the design accuracy either because the grain size of the second coat of powder paint, is very similar or identical to that of the first base coat of powder paint.
[0010] The procedure described in the European patent EP-0.818.248, comprises the following stages:
application of a first powder paint electrostatically charged for the adherence thereof to the metallic surface to be treated,
subjecting this profile to a first temperature of between 170° C and 200° C during an appropriate time in order to start the process of polymerisation of said paint with the object of fusing it and extending it homogeneously on the surface of said profile,
cooling this profile to halt the polymerisation process,
applying by screen printing a second powder paint of the same type of resin but with a hue or colour different to that of the first paint,
taking said profile to a final temperature for a certain time to obtain the complete polymerisation of this first and second coat of paint.
[0011] Conventionally the commercial paints applied in these procedures for protecting and decorating aluminium destined for the manufacture of doors and enclosures in general, are paints of polyester powder with a distribution in the size of particles of the powder that depends on each manufacturer, but which conventionally lies between 40 and 150 microns.
[0012] The experts in these techniques are aware that the size of the powder particles has a direct influence on the electrostatic deposition of the paint. During the decoration process it is necessary to manipulate the metallic piece, for example in a change of position of the piece to apply paint to another of its faces, whereby during said manipulation the particles of very small grain size suffer displacements which deform the decorative motif and impair the quality of the final result.
DESCRIPTION OF THE INVENTION
[0013] The procedure for decoration disclosed in the present invention, resolves satisfactorily the shortcomings of the procedures known at the present time, since it allows the decoration of metallic pieces with an extremely high degree of accuracy in the reproduction of decorative designs, and therefore it provides a finish of a quality much superior to the procedures for decoration known in the state of the art.
[0014] The procedure object of the invention starts from a first conventional stage, wherein a first polyester-based powder paint is deposited electrostatically on a metallic piece to be decorated, such as for example an aluminium or iron piece. Likewise in a conventional manner, this first powder paint is subjected to a heat treatment.
[0015] The innovation of the invention resides in the application by means of screen printing of a second powder paint with a particle size less than 40 microns, in contrast to habitual practice in these techniques, and all this with the object of achieving a very high definition in the reproduction of the decorative motif through the use of a very fine powder. In this way it is possible to reproduce details, like for example the grain of wood, with a precision that would not be possible with the procedures known at the present time.
[0016] Subsequently this second powder paint with a selected grain size, is subjected to a heat treatment in localised areas to fix it on the first paint. The heat treatment consists of the application of radiation, preferably an infrared radiation, with the object of heating the second paint until the same reaches a gelled state which produces its adherence on the first coat of base paint, and which in this way allows the manipulation of the metallic piece to be decorated without the risk of the particles of the second paint moving and deforming the decorative design.
[0017] Finally the metallic piece with the first base paint and the second paint, is subjected to a final and joint heat treatment whereby the first and the second coat of paint are polymerised together, the final decoration of the product being obtained.
[0018] The procedure object of the invention achieves in this way levels of definition in the reproduction of a decorative motif much superior to those obtained by means of conventional decoration techniques.
DESCRIPTION OF THE DRAWINGS
[0019] To complete the description that is being made and with the object of assisting in a better understanding of the characteristics of the invention, in accordance with a preferred example of practical embodiment thereof, attached as an integral part of said description, is a set of drawings wherein by way of illustration and not restrictively, the following has been represented:
Figure 1 shows schematically the elliptic reflector employed preferably in the heat treatment of the second paint participant in the procedure.
PREFERRED EMBODIMENT OF THE INVENTION
[0020] According to that explained above, the procedure for decoration object of the present invention comprises the following stages:
1. - Application of a first base paint of powdered polyester which is deposited electrostatically on the aluminium or iron piece which it is desired to decorate.
2. - Heat treatment of said first base paint by conventional means during a period of time lasting between 4 and 6 minutes at a temperature of 130° C.
3. - Application by means of screen printing of a second powder paint on said first base paint, forming a distribution of this second paint in accordance with the decorative motif it is desired to obtain, like for example wood, marble or any other design. With the object of obtaining a high degree of accuracy in the reproduction of the decorative design, the application of this second paint is carried out by means of a screen printing mesh of 40 microns mesh pitch, and the particles of this second powder paint are selected with a size less than 40 microns, since particles of greater size would not pass through the mesh and would block the pores thereof, losing definition therefore in the reproduction of the decorative motif. In a preferred embodiment of the invention the grain size of the particles of this second paint is of between 5 and 30 microns.
4. - Thereafter a heat treatment is carried out localised in the areas (A) where said
second paint has been deposited, with the object that the same acquires a gelled state
which allows its adherence on the first base paint. This heat treatment consists of
the application of an infrared radiation with a short wavelength having its maximum
energy located between 1000 and 1200 nm, being focussed and directed by an elliptic
reflector (2), with which, according to the arrangement shown in figure 1, the maximum
concentration of radiation is obtained at a distance (C) lying at between 10 and 30
mm from the surface of the metal (1). In a preferred embodiment this distance is of
between 15 and 17 mm.
The short wavelength is obtained by means of a quartz lamp working at 2400° C, and
the time of application of maximum radiation is of between 1 and 10 seconds, preferably
between 2 and 4 seconds. With these working parameters it is achieved that the time
necessary to complete this heat treatment by application of infrared radiation, is
very short, and therefore does not influence the total time in which the decoration
of a metallic piece is completed.
The object of applying the infrared radiation in a localised form in the areas where
the second paint has been applied, is in order not to affect the first base paint,
so that the state is not altered which this base paint has reached during its heat
treatment described in point 2.
This second paint can have a different hue or colour to that of the first base paint,
with the object of obtaining the desired decorative design.
At this point, the metallic piece to be treated can be manipulated, for example its
position can be changed in order to apply paint on another of its faces, without risk
that the particles of the second paint applied by screen printing move from the precise
point in which they have been deposited by means of the screen printing mesh.
The working parameters described for this stage of the procedure, were selected to
attain, in a certain time, a particular gelled state of the second paint, which without
delaying excessively the time necessary to complete the heat treatment, allow that
the gelled state reached is sufficient to impede the displacement of the particles
of the second paint.
5. - Finally after the application of the first and the second coat of paint with their respective heat treatments, that is, the lacquering of the first base paint and the adherence of the second paint, the whole undergoes a final heat treatment for polymerising jointly the two coats of paint. This final treatment is carried out at a temperature of between 160° C and 220° C (temperature of the metal) during a period of 8 to 20 minutes.